Mr. Lewin was aboard American Airlines Flight 11, a Boeing 767 that took off from Boston on Tuesday morning bound for Los Angeles. Flight 11 was hijacked and crashed into the World Trade Center's north tower at 8:48 a.m. Tuesday, 18 minutes before a second airliner crashed into the south tower.

In 1998, Mr. Lewin co-founded Akamai in Cambridge, Mass., along with Tom Leighton, now Akamai's chief scientist, and Jonathan Seelig, now Akamai's vice president for strategy and corporate development.

Using technology and algorithms developed by Mr. Lewin and others, Akamai devised one of the most efficient systems for accelerating the delivery of Internet information, especially Web pages. When a company becomes an Akamai customer, Akamai generally distributes significant information for the client's Web pages to a network of server computers around the nation.

Akamai has counted Apple, BestBuy.com, Nasdaq and Novartis among its customers.